1. Field of the Invention
The present invention generally relates to the formation of non-native films on surfaces of compound semiconductor films, and more particularly relates to the preparation of III-V semiconductor surfaces for deposition and the subsequent deposition of a film by the Atomic Layer Deposition (ALD) method.
2. Discussion of Related Art
For many decades compound semiconductor materials, such as those formed from alloys of group III atoms with group V atoms (III-V semiconductors), have found limited application in microelectronics primarily because the native oxide which forms on these materials is of very poor quality relative to the native oxide which forms on homogeneous group IV semiconductors, such as silicon (Si). This relatively poor quality of the native oxide degrades the electrical performance of microelectronic devices fabricated from III-V semiconductors. For example, because the native oxide of compound semiconductor devices is a leaky insulator, it has not been possible to form high quality metal oxide semiconductor field effect transistors (MOSFET) with the native oxide as a gate dielectric. Thus, to date, only bipolar junction transistors (BJT) and junction field effect transistors (JFET) are commercially fabricated in high volume from compound semiconductor materials, neither of which provides all of the many of the advantages of the MOSFET.
Meanwhile, while the good electrical quality of the native oxide of silicon (silicon dioxide) has enabled the rapid scaling of silicon-based MOSFET transistors over many decades, device dimensions have reached the point where the thickness of silicon dioxide in the MOSFET gate dielectric is only a few monolayers and has therefore also become unacceptably leaky. Thus, advancement of silicon MOSFET fabrication has reached the point where the native oxide of silicon is just as inadequate as that of the native oxide of compound semiconductors. In response, the gate dielectric in the silicon MOSFET has begun to migrate from the native oxide of silicon to a non-native, high dielectric constant (high-K) material, such as hafnium oxide (HfO2), deposited on the silicon surface by chemical vapor deposition (CVD) or a variant thereof typically referred to as atomic layer deposition (ALD).
The success of high-k gate dielectric formation by ALD on silicon has attracted interest in the application of high-k gate dielectrics to compound semiconductor MOSFETS. However, as shown in FIG. 1, it remains difficult to provide a surface on the compound semiconductor substrate, such as III-V substrate 101, enabling an ALD process to form a high quality dielectric film. In particular, the presence of even a few monolayers of the poor quality native oxide 105 on III-V substrate 101 prior to ALD of high-k dielectric 110 is high highly detrimental to the performance of a microelectronic device. Because there is currently no means to provide for high-k dielectric 110 directly on III-V substrate 101 without poor quality native oxide 105, the detrimental properties of native oxide 105 continue to result in a gate dielectric unsuitable for high performance transistors.